If $a + b = 10$ and $x + y = 8$, what is $7a - y - x + 7b$ ?
$= 7a + 7b - x - y$ $= (7) \cdot (a + b) + (-1) \cdot (x + y)$ $= (7) \cdot (10) + (-1) \cdot (8)$ $= 70 - 8$ $= 62$